1. The Field of the Invention
The present invention relates to inducing transverse motion at the end of a needle attached to a Langevin transducer horn. More specifically, the present invention relates to an improved Langevin transducer that induces transverse motion along with longitudinal motion.
2. State of the Art
Cataracts are the leading cause of blindness in the world. It is estimated that in the United States, age-related lenticular changes have been reported in 42% of those between 52 and 64, 60% of people between 65 and 74 and 91% of people between 75 and 85. A cataract is an opacity or cloudiness in the lens of the eye.
To address these issues, it has been common for a number of years to remove the lens of the eye. Initially this was done by making a large incision to facilitate removal of the lens and in some cases, replacing the lens with an implant.
In modern cataract surgery, phacoemulsification is a common procedure to facilitate removal of the damaged lens. Phacoemulsification involves using an ultrasonic handpiece to emulsify the cataract in the eye while the eye is irrigated with a balanced salt solution. The emulsified lens is aspirated and a prosthetic intraocular lens implant is inserted where the original lens was. This procedure has substantially reduced the size of the incision necessary in the eye and has significantly reduced recuperation time for patients.
In a conventional phacoemulsification handpiece, a hollow, resonating horn and a hollow needle attached thereto are disposed in communication with an aspirating line which suctions emulsified material through the center of the horn. The horn is disposed in a housing which typically includes an irrigation portion for introducing fluid around the horn and into the patient's eye.
A number of piezoelectric elements (often ceramic piezoelectric elements), typically referred to as a stack, are disposed adjacent each other about the horn. When the piezoelectric stack is subjected to an oscillating voltage, the ceramic piezoelectric elements expand and contract, thereby causing rapid longitudinal movement (i.e. longitudinal vibration at ultrasonic frequencies) in the horn and thereby in a needle which is attached at a distal end of the horn. The longitudinal vibration is used to emulsify the cataractous lens, allowing the cataract to be removed.
It is believed that transverse motion of the hand piece tip aids in phacoemulsification. There have been numerous attempts to create transverse motion during tissue removal. See e.g. U.S. Pat. No. 6,402,769 (Boukhny et al); U.S. Pat. No. 5,722,945 (Anis et al.); U.S. Pat. No. 5,222,959 (Anis et al); U.S. Pat. No. 4,504,264 (Kelman); and U.S. Patent Pub. 2006/0041220. In order to achieve out-of-plane motion in the horn, other inventors have created torsional motion in the horn and converted the torsional motion to transverse motion via a special bent needle. This torsional motion may be created through a separate ceramic stack, a configuration creating torsional motion with the stack or through slits made in the horn which change the geometry of the transducer. These methods introduce mechanical loss through conversion of torsional motion to transverse motion and appear to increase costs, and require the use of a bent needle to convert the torsional motion to a transverse motion. Furthermore, each requires changes to conventional handpiece design.
Thus, there is a need for a method for producing transverse movement in the horn and/or a needle attached to a horn. Preferably, such a method should be relatively low cost, not require major changes to existing handpiece design, and work with existing needles.